High-resolution sequence stratigraphic framework of carbonate deposition controlled by sea level and geostrophic bottom currents, south Florida platform margin

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:6135830

Locker, S D; Hine, A C ^[1]; Shinn, E A ^[2]

---

1. Univ. of South Florida, St. Petersburg, FL (United States)
2. Geological Survey, St. Petersburg, FL (United States)

High-resolution seismic reflection profiles seaward of the Marquesas Keys reveal at least eight late Quaternary sequences which downlap onto the Miocene ( ) age Pourtales Terrace at 250 m water depth. Inferred correlations are presented between these sequences and the last 7--8 sea-level cycles during the past 150 ky. The setting is unusual in that the present reef-rimmed, shallow inner shelf supplies minimal sediment to the adjacent margin where over 30 m of Holocene sediment has accumulated on portions of the outer shelf and slope. Seaward of the inner-shelf reef'' barrier, an outer-shelf terrace in 50--60 m water depth forms the upper boundary of the prograding late Quaternary sequences. These sequences exhibit both current-controlled internal geometries (e.g., sediment drifts) and sea-level controlled features such as lowstand slope erosion, transgressive unconformities, and paleoshorelines or reefs formed during lower stands of sea level. Bottom currents also severely eroded the slope at times, creating prominent unconformities. These 5th-6th order depositional sequences exhibit many features outlined by the Exxon sequence stratigraphy models. Systems tracts inferred from seismic records include lowstand wedge, shelf margin, and highstand deposits. Transgressive systems tracts are more difficult to identify and correspond to the flat outer-shelf terrace that experienced rapid lateral transgressions and regressions of sea level, and was exposed to subaerial processes during low stands. This study provides new insight on the importance of both geostrophic boundary currents and sea-level change in controlling stratigraphic development of a carbonate platform margin. Locally-thick accumulations off the Marquesas Keys may demonstrate sedimentation in response to a persistent cold cyclonic gyre in this area which causes weak counter-currents in an otherwise strong geostrophic current area.

• OSTI ID: 6135830
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CARBONATE ROCKS
CENOZOIC ERA
CONTINENTAL MARGIN
CURRENTS
DEPOSITION
DEVELOPED COUNTRIES
FLORIDA
FLUCTUATIONS
GEOLOGIC AGES
GEOLOGY
GEOMORPHOLOGY
GEOPHYSICAL SURVEYS
LEVELS
NORTH AMERICA
QUATERNARY PERIOD
REFLECTION
ROCKS
SEA LEVEL
SEDIMENTARY ROCKS
SEISMIC SURVEYS
STRATIGRAPHY
SURVEYS
USA
VARIATIONS
WATER CURRENTS